I really like how the music grows along with your upgrades.
The UI is really-really clever and nice-looking, and you can learn how to play without any tutorials.
Really like the art style (with that clever pattern) and the small "gif" animations too. I miss a final big illustration as a reward for completing it tho.
The only sad thing is that if you "let the game be", it will finish by itself anyway so, there is no really a challenge to overcome :( . Could also be my jealousness speaking after finished it twice XD.